libstdc++
typeinfo
1 // RTTI support for -*- C++ -*-
2 // Copyright (C) 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002,
3 // 2003, 2004, 2005, 2006, 2007, 2009
4 // Free Software Foundation
5 //
6 // This file is part of GCC.
7 //
8 // GCC is free software; you can redistribute it and/or modify
9 // it under the terms of the GNU General Public License as published by
10 // the Free Software Foundation; either version 3, or (at your option)
11 // any later version.
12 //
13 // GCC is distributed in the hope that it will be useful,
14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 // GNU General Public License for more details.
17 //
18 // Under Section 7 of GPL version 3, you are granted additional
19 // permissions described in the GCC Runtime Library Exception, version
20 // 3.1, as published by the Free Software Foundation.
21 
22 // You should have received a copy of the GNU General Public License and
23 // a copy of the GCC Runtime Library Exception along with this program;
24 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
25 // <http://www.gnu.org/licenses/>.
26 
27 /** @file typeinfo
28  * This is a Standard C++ Library header.
29  */
30 
31 #ifndef _TYPEINFO
32 #define _TYPEINFO
33 
34 #include <exception>
35 
36 #pragma GCC visibility push(default)
37 
38 extern "C++" {
39 
40 namespace __cxxabiv1
41 {
42  class __class_type_info;
43 } // namespace __cxxabiv1
44 
45 // Determine whether typeinfo names for the same type are merged (in which
46 // case comparison can just compare pointers) or not (in which case
47 // strings must be compared and g++.dg/abi/local1.C will fail), and
48 // whether comparison is to be implemented inline or not. By default we
49 // use inline pointer comparison if weak symbols are available, and
50 // out-of-line strcmp if not. Out-of-line pointer comparison is used
51 // where the object files are to be portable to multiple systems, some of
52 // which may not be able to use pointer comparison, but the particular
53 // system for which libstdc++ is being built can use pointer comparison;
54 // in particular for most ARM EABI systems, where the ABI specifies
55 // out-of-line comparison. Inline strcmp is not currently supported. The
56 // compiler's target configuration can override the defaults by defining
57 // __GXX_TYPEINFO_EQUALITY_INLINE to 1 or 0 to indicate whether or not
58 // comparison is inline, and __GXX_MERGED_TYPEINFO_NAMES to 1 or 0 to
59 // indicate whether or not pointer comparison can be used.
60 
61 #ifndef __GXX_MERGED_TYPEINFO_NAMES
62  #if !__GXX_WEAK__
63  // If weak symbols are not supported, typeinfo names are not merged.
64  #define __GXX_MERGED_TYPEINFO_NAMES 0
65  #else
66  // On platforms that support weak symbols, typeinfo names are merged.
67  #define __GXX_MERGED_TYPEINFO_NAMES 1
68  #endif
69 #endif
70 
71 // By default follow the same rules as for __GXX_MERGED_TYPEINFO_NAMES.
72 #ifndef __GXX_TYPEINFO_EQUALITY_INLINE
73  #if !__GXX_WEAK__
74  #define __GXX_TYPEINFO_EQUALITY_INLINE 0
75  #else
76  #define __GXX_TYPEINFO_EQUALITY_INLINE 1
77  #endif
78 #endif
79 
80 namespace std
81 {
82  /**
83  * @brief Part of RTTI.
84  *
85  * The @c type_info class describes type information generated by
86  * an implementation.
87  */
88  class type_info
89  {
90  public:
91  /** Destructor first. Being the first non-inline virtual function, this
92  * controls in which translation unit the vtable is emitted. The
93  * compiler makes use of that information to know where to emit
94  * the runtime-mandated type_info structures in the new-abi. */
95  virtual ~type_info();
96 
97  /** Returns an @e implementation-defined byte string; this is not
98  * portable between compilers! */
99  const char* name() const
100  { return __name; }
101 
102 #if !__GXX_TYPEINFO_EQUALITY_INLINE
103  bool before(const type_info& __arg) const;
104 
105  // In old abi, or when weak symbols are not supported, there can
106  // be multiple instances of a type_info object for one
107  // type. Uniqueness must use the _name value, not object address.
108  bool operator==(const type_info& __arg) const;
109 #else
110  #if !__GXX_MERGED_TYPEINFO_NAMES
111  #error "Inline implementation of type_info comparision requires merging of type_info objects"
112  #endif
113  /** Returns true if @c *this precedes @c __arg in the implementation's
114  * collation order. */
115  // In new abi we can rely on type_info's NTBS being unique,
116  // and therefore address comparisons are sufficient.
117  bool before(const type_info& __arg) const
118  { return __name < __arg.__name; }
119 
120  bool operator==(const type_info& __arg) const
121  { return __name == __arg.__name; }
122 #endif
123  bool operator!=(const type_info& __arg) const
124  { return !operator==(__arg); }
125 
126  // Return true if this is a pointer type of some kind
127  virtual bool __is_pointer_p() const;
128 
129  // Return true if this is a function type
130  virtual bool __is_function_p() const;
131 
132  // Try and catch a thrown type. Store an adjusted pointer to the
133  // caught type in THR_OBJ. If THR_TYPE is not a pointer type, then
134  // THR_OBJ points to the thrown object. If THR_TYPE is a pointer
135  // type, then THR_OBJ is the pointer itself. OUTER indicates the
136  // number of outer pointers, and whether they were const
137  // qualified.
138  virtual bool __do_catch(const type_info *__thr_type, void **__thr_obj,
139  unsigned __outer) const;
140 
141  // Internally used during catch matching
142  virtual bool __do_upcast(const __cxxabiv1::__class_type_info *__target,
143  void **__obj_ptr) const;
144 
145  protected:
146  const char *__name;
147 
148  explicit type_info(const char *__n): __name(__n) { }
149 
150  private:
151  /// Assigning type_info is not supported.
152  type_info& operator=(const type_info&);
153  type_info(const type_info&);
154  };
155 
156  /**
157  * @brief Thrown during incorrect typecasting.
158  * @ingroup exceptions
159  *
160  * If you attempt an invalid @c dynamic_cast expression, an instance of
161  * this class (or something derived from this class) is thrown. */
162  class bad_cast : public exception
163  {
164  public:
165  bad_cast() throw() { }
166 
167  // This declaration is not useless:
168  // http://gcc.gnu.org/onlinedocs/gcc-3.0.2/gcc_6.html#SEC118
169  virtual ~bad_cast() throw();
170 
171  // See comment in eh_exception.cc.
172  virtual const char* what() const throw();
173  };
174 
175  /**
176  * @brief Thrown when a NULL pointer in a @c typeid expression is used.
177  * @ingroup exceptions
178  */
179  class bad_typeid : public exception
180  {
181  public:
182  bad_typeid () throw() { }
183 
184  // This declaration is not useless:
185  // http://gcc.gnu.org/onlinedocs/gcc-3.0.2/gcc_6.html#SEC118
186  virtual ~bad_typeid() throw();
187 
188  // See comment in eh_exception.cc.
189  virtual const char* what() const throw();
190  };
191 } // namespace std
192 
193 #pragma GCC visibility pop
194 
195 } // extern "C++"
196 #endif